Disorders of CSF hydrodynamics

Toward the "Perfect" Shunt: Historical Vignette, Current Efforts, and Future Directions

As a concept, drainage of excess fluid volume in the cranium has been around for more than 1000 years. Starting with the original decompression-trepanation of Abulcasis to modern programmable shunt systems, to other nonshunt-based treatments such as endoscopic third ventriculostomy and choroid plexus cauterization, we have come far as a field. However, there are still fundamental limitations that shunts have yet to overcome: namely posture-induced over- and underdrainage, the continual need for valve opening pressure especially in pediatric cases, and the failure to reinstall physiologic intracranial pressure dynamics. However, there are groups worldwide, in the clinic, in industry, and in academia, that are trying to ameliorate the current state of the technology within hydrocephalus treatment. This chapter aims to provide a historical overview of hydrocephalus, current challenges in shunt design, what members of the community have done and continue to do to address these challenges, and finally, a definition of the "perfect" shunt is provided and how the authors are working toward it.

Right Transcephalic Ventriculo-Subclavian Shunt in the Surgical Treatment of Hydrocephalus-An Original Procedure for Drainage of Cerebrospinal Fluid into the Venous System

The objectives of this article are to present an original surgical procedure for the temporary or definitive resolution of hydrocephalus, in the case of repeated failure of standard treatment techniques, and to present a case that was resolved using this surgical technique.

MATERIALS AND METHODS

We present the case of a 20-year-old male patient with congenital hydrocephalus who underwent a number of 39 shunt revisions, given the repetitive dysfunctions of various techniques (ventriculo-peritoneal shunt, ventriculo-cardiac shunt). The patient was evaluated with the ventricular catheter externalized at the distal end and it was necessary to find an emergency surgical solution, considering the imminent risk of meningitis. The patient was also associated with the diagnosis of acute lithiasic cholecystitis.

RESULTS AND DISCUSSIONS

The final chosen solution, right ventriculo-venous drainage using the cephalic vein, was a temporary surgical solution, but there are signs that this procedure can provide long-term ventricular drainage.

CONCLUSIONS

Transcephalic ventriculo-subclavian drainage represents an alternative technical option, which can be used when established options become ineffective.

A mathematical framework for the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid

BACKGROUND

Shedding light on less-known aspects of intracranial fluid dynamics may be helpful to understand the hydrocephalus mechanism. The present study suggests a mathematical framework based on in vivo inputs to compare the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid (CSF) between the healthy subject and the hydrocephalus patient.

METHOD

The input data for the mathematical formulations was pulsatile blood velocity, which was measured using cine PC-MRI. Tube law was used to transfer the created deformation by blood pulsation in the vessel circumference to the brain domain. The pulsatile deformation of brain tissue with respect to time was calculated and considered to be inlet velocity in the CSF domain. The governing equations in all three domains were continuity, Navier-Stokes, and concentration. We used Darcy law with defined permeability and diffusivity values to define the material properties in the brain.

RESULTS

We validated the preciseness of the CSF velocity and pressure through the mathematical formulations with cine PC-MRI velocity, experimental ICP, and FSI simulated velocity and pressure. We used the analysis of dimensionless numbers including Reynolds, Womersley, Hartmann, and Peclet to evaluate the characteristics of the intracranial fluid flow. In the mid-systole phase of a cardiac cycle, CSF velocity had the maximum value and CSF pressure had the minimum value. The maximum and amplitude of CSF pressure, as well as CSF stroke volume, were calculated and compared between the healthy subject and the hydrocephalus patient.

CONCLUSION

The present in vivo-based mathematical framework has the potential to gain insight into the less-known points in the physiological function of intracranial fluid dynamics and the hydrocephalus mechanism.

Cerebrospinal fluid and blood profiles of transfer RNA fragments show age, sex, and Parkinson's disease-related changes

Transfer RNA fragments (tRFs) have recently been shown to be an important family of small regulatory RNAs with diverse functions. Recent reports have revealed modified tRF blood levels in a number of nervous system conditions including epilepsy, ischemic stroke, and neurodegenerative diseases, but little is known about tRF levels in the cerebrospinal fluid (CSF). To address this issue, we studied age, sex, and Parkinson's disease (PD) effects on the distributions of tRFs in the CSF and blood data of healthy controls and PD patients from the NIH and the Parkinson's Progression Markers Initiative (PPMI) small RNA-seq datasets. We discovered that long tRFs are expressed in higher levels in the CSF than in the blood. Furthermore, the CSF showed a pronounced age-associated decline in the level of tRFs cleaved from the 3'-end and anti-codon loop of the parental tRNA (3'-tRFs, i-tRFs), and more pronounced profile differences than the blood profiles between the sexes. In comparison, we observed moderate age-related elevation of blood 3'-tRF levels. In addition, distinct sets of tRFs in the CSF and in the blood segregated PD patients from controls. Finally, we found enrichment of tRFs predicted to target cholinergic mRNAs (Cholino-tRFs) among mitochondrial-originated tRFs, raising the possibility that the neurodegeneration-related mitochondrial impairment in PD patients may lead to deregulation of their cholinergic tone. Our findings demonstrate that the CSF and blood tRF profiles are distinct and that the CSF tRF profiles are modified in a sex-, age-, and disease-related manner, suggesting that they reflect the inter-individual cerebral differences and calling for incorporating this important subset of small RNA regulators into future studies.

Communicating hydrocephalus and raised intracranial pressure in association with multi-systemic smooth muscle dysfunction syndrome (MSMDS)

Multi-systemic smooth muscle dysfunction syndrome (MSMDS) is extremely rare and can manifest in multiple ways. Associated hydrocephalus has not yet been reported. Here, we report a three-year-old girl with communicating hydrocephalus and raised intracranial pressure secondary to MSMDS. Pathological mechanisms are proposed, as is the need to investigate patients diagnosed with MSMDS for ventriculomegaly and raised pressure.

Noninvasive methods to monitor intracranial pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) is determined by the production of and outflow facility of cerebrospinal fluid. Since alterations in ICP are implicated in several vision-threatening and life-threatening diseases, measurement of ICP is necessary and common. All current clinical methods to measure ICP are invasive and carry the risk for significant side effects. Therefore, the development of accurate, reliable, objective, and portal noninvasive devices to measure ICP has the potential to change the practice of medicine. This review discusses recent advances and barriers to the clinical implementation of noninvasive devices to determine ICP.

RECENT FINDINGS

Many noninvasive methods to determine ICP have been developed. Although most have significant limitations limiting their clinical utility, several noninvasive methods have shown strong correlations with invasively obtained ICP and have excellent potential to be developed further to accurately quantify ICP and ICP changes.

SUMMARY

Although invasive methods remain the mainstay for ICP determination and monitoring, several noninvasive biomarkers have shown promise to quantitatively assess and monitor ICP. With further refinement and advancement of these techniques, it is highly possible that noninvasive methods will become more commonplace and may complement or even supplant invasively obtained methods to determine ICP in certain situations.

Computational fluid dynamics model to predict the dynamical behavior of the cerebrospinal fluid through implementation of physiological boundary conditions

Cerebrospinal fluid (CSF) dynamics play an important role in maintaining a stable central nervous system environment and are influenced by different physiological processes. Multiple studies have investigated these processes but the impact of each of them on CSF flow is not well understood. A deeper insight into the CSF dynamics and the processes impacting them is crucial to better understand neurological disorders such as hydrocephalus, Chiari malformation, and intracranial hypertension. This study presents a 3D computational fluid dynamics (CFD) model which incorporates physiological processes as boundary conditions. CSF production and pulsatile arterial and venous volume changes are implemented as inlet boundary conditions. At the outlets, 2-element windkessel models are imposed to simulate CSF compliance and absorption. The total compliance is first tuned using a 0D model to obtain physiological pressure pulsations. Then, simulation results are compared with in vivo flow measurements in the spinal subarachnoid space (SAS) and cerebral aqueduct, and intracranial pressure values reported in the literature. Finally, the impact of the distribution of and total compliance on CSF pressures and velocities is evaluated. Without respiration effects, compliance of 0.17 ml/mmHg yielded pressure pulsations with an amplitude of 5 mmHg and an average value within the physiological range of 7-15 mmHg. Also, model flow rates were found to be in good agreement with reported values. However, when adding respiration effects, similar pressure amplitudes required an increase of compliance value to 0.51 ml/mmHg, which is within the range of 0.4-1.2 ml/mmHg measured in vivo. Moreover, altering the distribution of compliance over the four different outlets impacted the local flow, including the flow through the foramen magnum. The contribution of compliance to each outlet was directly proportional to the outflow at that outlet. Meanwhile, the value of total compliance impacted intracranial pressure. In conclusion, a computational model of the CSF has been developed that can simulate CSF pressures and velocities by incorporating boundary conditions based on physiological processes. By tuning these boundary conditions, we were able to obtain CSF pressures and flows within the physiological range.

Elevated cerebrospinal fluid protein levels associated with poor short-term outcomes after spinal cord stimulation in patients with disorders of consciousness

Background

Spinal cord stimulation (SCS) is a promising treatment for patients with disorders of consciousness (DoC); however, the laboratory examinations and different electrodes (permanent #39286 vs. temporary percutaneous #3777, Medtronic, USA) that are associated with postoperative outcomes are unclear. The study aims to study the association between the change in postoperative cerebrospinal fluid (CSF) protein level and improvement in consciousness after SCS in DoC patients and to explore whether different electrodes were associated with elevated CSF protein levels.

Materials and methods

A total of 66 DoC patients who received SCS treatment from December 2019 to December 2021 were retrospectively analyzed. Patients were grouped according to their elevated CSF protein level. The clinical characteristics of the patients and SCS stimulation parameters were compared. The preoperative sagittal diameter of the spinal canal is the distance from the midpoint of the posterior border of the vertebral body to the midpoint of the posterior wall of the spinal canal at the level of the superior border of C3. The postoperative sagittal diameter of the spinal canal is the distance from the midpoint of the posterior edge of the vertebral body to the anterior edge of the stimulation electrode. Patients with improved postoperative CRS-R scores greater than 3 or who progressed to the MCS + /eMCS were classified as the improved group and otherwise regarded as poor outcome.

Results

We found that more DoC patients had elevated CSF protein levels among those receiving SCS treatment with permanent electrodes than temporary percutaneous electrodes (P = 0.001), and elevated CSF protein levels were significantly associated with a reduced sagittal diameter (P = 0.044). In DoC patients receiving SCS treatment, we found that elevated CSF protein levels (P = 0.022) and preoperative diagnosis (P = 0.003) were significantly associated with poor outcomes at 3 months. Logistic regression analysis showed that elevated CSF protein levels were significantly associated with poor outcomes (OR 1.008, 95% CI 1.001–1.016, P = 0.032).

Conclusion

The results suggest that reducing the effect of electrode pads on anatomical changes may help improve the outcomes of DoC patients receiving SCS treatment. CSF protein levels are associated with poor postoperative outcomes and whether they are potential biomarkers in DoC patients receiving SCS treatment remain further exploration.

Association of Atrial Fibrillation and Cardioembolic Stroke with Poststroke Delirium Susceptibility: A Systematic Review and Meta-Analysis of Observational Studies

BACKGROUND

Several studies have shown atrial fibrillation (AF) and cardioembolic stroke (CES) to be associated with the risk of poststroke delirium (PSD). However, other studies have reported inconsistent results. We performed a comprehensive meta-analysis to clarify the associations between AF and CES and PSD susceptibility.

METHODS

We searched relevant studies meeting inclusion criteria in PubMed, Google Scholar, and Web of Science. Useful data were pooled, and odds ratios and 95% confidence intervals were calculated. We also assessed heterogeneity among studies, performed sensitivity analyses, and estimated publication bias.

RESULTS

This meta-analysis containing 18 observational studies proved that AF (odds ratio =2.30, 95% confidence interval = 2.00-2.65, P < 0.0001) was associated with an increased risk of PSD. CES was also found to have a higher risk of delirium compared with other types of stroke based on the Trial of Org 10172 in Acute Stroke Treatment classification (odds ratio = 2.02, 95% confidence interval = 1.47-2.79, P < 0.0001).

CONCLUSIONS

Our meta-analysis suggested that AF and CES contribute to increased risk of PSD.

Predictive Values for Time from Transducer Stopcock Closure to Accurate Intracranial Pressure Reading

BACKGROUND

When using an external ventricular drain (EVD) to monitor intracranial pressure (ICP), nurses need to know how long to wait after each manipulation of the transducer before the displayed ICP value represents an accurate signal. This study explores ICP signal equilibration time (EqT) under clinical conditions.

METHODS

This was a prospective ex vivo study using a simulated skull, standard EVD tubing, and a strain gauge transducer. All 270 trials simulating 90 combinations of different pressures and common clinical conditions were completed in August 2021. Each trial was recorded on video. Videos were scored using video editing software to obtain the exact start and stop time for each trial.

RESULTS

The mean EqT was 44.90 (18.77) seconds. One hundred fifty (55.56%) observations did not reach their expected value within 60 s. The longest mean EqTs were noted when blood was present in the EVD tubing (57.67 [8.91] seconds), when air bubbles were in the tubing (57.41 [8.73] seconds), and when EVD tubing was not flat (level) (50.77 [15.43] seconds). An omnibus test comparing mean EqT for conditions with no variables manipulated (30.08 [16.07] seconds) against mean EqT for all others (47.18 [18.13] seconds) found that mean EqTs were significantly different (P < 0.001).

CONCLUSIONS

Even when no additional variables were introduced, the mean EqTs were ~ 30 s. Common clinical variables increase the length of time before a transducer connected to an EVD will provide an accurate reading. Nurses should wait at least 30 s after turning the EVD stopcock before assuming ICP value reflects accurate ICP.

Zero retinal vein pulsation amplitude extrapolated model in non-invasive intracranial pressure estimation

Intracranial pressure (ICP) includes the brain, optic nerve, and spinal cord pressures; it influences blood flow to those structures. Pathological elevation in ICP results in structural damage through various mechanisms, which adversely affects outcomes in traumatic brain injury and stroke. Currently, invasive procedures which tap directly into the cerebrospinal fluid are required to measure this pressure. Recent fluidic engineering modelling analogous to the ocular vascular flow suggests that retinal venous pulse amplitudes are predictably influenced by downstream pressures, suggesting that ICP could be estimated by analysing this pulse signal. We used this modelling theory and our photoplethysmographic (PPG) retinal venous pulse amplitude measurement system to measure amplitudes in 30 subjects undergoing invasive ICP measurements by lumbar puncture (LP) or external ventricular drain (EVD). We estimated ICP from these amplitudes using this modelling and found it to be accurate with a mean absolute error of 3.0 mmHg and a slope of 1.00 (r = 0.91). Ninety-four percent of differences between the PPG and invasive method were between − 5.5 and + 4.0 mmHg, which compares favourably to comparisons between LP and EVD. This type of modelling may be useful for understanding retinal vessel pulsatile fluid dynamics and may provide a method for non-invasive ICP measurement.

Influence of interaction of cerebral fluids on ventricular deformation: A mathematical approach

This paper describes the effects of the interaction of cerebral fluids (arterial, capillary and venous blood, cerebrospinal fluid) on ventricular wall displacement and periventricular pressure using a mathematical multiphase poroelasticity model for the cerebral parenchyma. The interaction of cerebral fluids is given by a set of four numerical coefficients. A multiple linear regression with interaction is constructed that allows us to quantify the effect of these coefficients on the average ventricular wall displacement. The prevailing influence of an arterial-liquor component was observed. The sets of coefficients associated with such pathological conditions were found: normal pressure hydrocephalus, intracranial hypertension, and replacement ventriculomegaly under a prolonged hypoperfusion.

Utility of True Fast Imaging with Steady-State Precession in Detecting Arachnoid Veils of the Posterior Fossa

INTRODUCTION

Arachnoid membranes are well recognized as a cause of cerebrospinal fluid (CSF) flow impairment in disorders such as obstructive hydrocephalus and syringohydromyelia, but can be difficult to detect with standard noninvasive imaging techniques. True fast imaging with steady-state precession (TrueFISP) can exhibit brain pulsations and CSF dynamics with high spatiotemporal resolution. Here, we demonstrate the utility of this technique in the diagnosis and management of arachnoid membranes in the posterior fossa.

CASE PRESENTATIONS

Three symptomatic children underwent cine TrueFISP imaging for suspicion of CSF membranous obstruction. Whereas standard imaging failed to or did not clearly visualize the site of an obstructive lesion, preoperative TrueFISP identified a membrane in all 3 cases. The membranes were confirmed intraoperatively, and postoperative TrueFISP helped verify adequate marsupialization and recommunication of CSF flow. Two out of the 3 cases showed a decrease in cerebellar tonsillar pulsatility following surgery. All children showed symptomatic improvement.

CONCLUSION

TrueFISP is able to detect pulsatile arachnoid membranes responsible for CSF outflow obstruction that are otherwise difficult to visualize using standard imaging techniques. We advocate use of this technology in pre- and postsurgical decision-making as it provides a more representative image of posterior fossa pathology and contributes to our understanding of CSF flow dynamics. There is potential to use this technology to establish prognostic biomarkers for disorders of CSF hydrodynamics.

Cerebrospinal fluid hydrodynamics in arachnoid cyst patients with persistent idiopathic intracranial hypertension: A case series and review

Background:

A clear connection has been established between arachnoid cysts (ACs) and the evolution of idiopathic intracranial hypertension (IIH), a connection, which is presently not well understood. Cerebrospinal fluid (CSF) is an integral element of this condition. Little is known about either the influence of AC on CSF hydrodynamics or the specific nature of CSF, which contributes to the complex pathology of IIH.

Case Description:

This study aimed to chronicle in detail four patients with previously treated intracranial ACs, who developed persistent IIH. This series and review aims to identify and qualitatively analyze the multiple constituents, which could possibly elucidate the intrinsic relationship between arachnoid cyst-induced IIH and CSF hydrodynamics. A retrospective analysis of the medical records of four patients admitted to the institution’s neurosurgery department during the period of 1994–2013 was completed. This study investigated discernible aspects linking CSF pathophysiology with the development of IIH in AC patients. Four male patients, ranging from 3 to 44 years of age at presentation, had a left-sided arachnoid cyst treated surgically. All four patients subsequently developed IIH. Three patients remain persistently symptomatic.

Conclusion:

IIH associated with AC is a hydrodynamic disorder. The full discovery of its fluctuant pathophysiology is the only way to identify an effective standard for the management and treatment of this condition.

Factors involved in the development of subdural hygroma after decompressive craniectomy for traumatic brain injury. A systematic review and meta-analysis

Subdural hygroma (SDG) represents a common complication following decompressive craniectomy (DC). To our knowledge we present the first meta-analysis investigating the role of clinical and technical factors in the development of SDG after DC for traumatic brain injury. We further investigated the impact of SDG on the final prognosis of patients. The systematic review of the literature was done according to the PRISMA guidelines. Two different online medical databases (PubMed/Medline and Scopus) were screened. Four articles were included in this meta-analysis. Data regarding age, sex, trauma dynamic, Glasgow Coma Scale (GCS), pupil reactivity and CT scan findings on admission were collected for meta-analysis in order to evaluate the possible role in the SDG formation. Moreover we studied the possible impact of SDG on the outcome by evaluating the rate of patients dead at final follow-up and the Glasgow Outcome Scale (GOS) at final follow-up. Among the factors available for meta-analysis only the basal cistern involvement on CT scan was associated with the development of a SDG after DC (p < 0.001). Moreover, patients without SDG had a statistically significant better outcome compared with patients who developed SDG after DC in terms of GOS (p < 0.001). The rate of patients dead at follow-up was lower in the group of patients without SDH (8.25%) compared with patients who developed SDG (11.51%). SDG after DC is a serious complication affecting the prognosis of patients. Further studies are needed to define the role of some adjustable technical aspect of DC in preventing such a complication.

Altered folate binding protein expression and folate delivery are associated with congenital hydrocephalus in the hydrocephalic Texas rat

Hydrocephalus (HC) is an imbalance in cerebrospinal fluid (CSF) secretion/absorption resulting in fluid accumulation within the brain with consequential pathophysiology. Our research has identified a unique cerebral folate system in which depletion of CSF 10-formyl-tetrahydrofolate-dehydrogenase (FDH) is associated with cortical progenitor cell-cycle arrest in hydrocephalic Texas (H-Tx) rats. We used tissue culture, immunohistochemistry, in-situ PCR and RT-PCR and found that the in-vitro proliferation of arachnoid cells is highly folate-dependent with exacerbated proliferation occurring in hydrocephalic CSF that has low FDH but high folate-receptor-alpha (FRα) and folate. Adding FDH to this CSF prevented aberrant proliferation indicating a regulatory function of FDH on CSF folate concentration. Arachnoid cells have no detectable mRNA for FRα or FDH, but FDH mRNA is found in the choroid plexus (CP) and CSF microvesicles. Co-localization of FDH, FRα and folate suggests important functions of FDH in cerebral folate transport, buffering and function. In conclusion, abnormal CSF levels of FDH, FRα and folate inhibit cortical cell proliferation but allow uncontrolled arachnoid cell division that should increase fluid absorption by increasing the arachnoid although this fails in the hydrocephalic brain. FDH appears to buffer available folate to control arachnoid proliferation and function.

Cerebrospinal fluid dynamics and intracranial pressure elevation in neurological diseases

The fine balance between the secretion, composition, volume and turnover of cerebrospinal fluid (CSF) is strictly regulated. However, during certain neurological diseases, this balance can be disrupted. A significant disruption to the normal CSF circulation can be life threatening, leading to increased intracranial pressure (ICP), and is implicated in hydrocephalus, idiopathic intracranial hypertension, brain trauma, brain tumours and stroke. Yet, the exact cellular, molecular and physiological mechanisms that contribute to altered hydrodynamic pathways in these diseases are poorly defined or hotly debated. The traditional views and concepts of CSF secretion, flow and drainage have been challenged, also due to recent findings suggesting more complex mechanisms of brain fluid dynamics than previously proposed. This review evaluates and summarises current hypotheses of CSF dynamics and presents evidence for the role of impaired CSF dynamics in elevated ICP, alongside discussion of the proteins that are potentially involved in altered CSF physiology during neurological disease. Undoubtedly CSF secretion, absorption and drainage are important aspects of brain fluid homeostasis in maintaining a stable ICP. Traditionally, pharmacological interventions or CSF drainage have been used to reduce ICP elevation due to over production of CSF. However, these drugs are used only as a temporary solution due to their undesirable side effects. Emerging evidence suggests that pharmacological targeting of aquaporins, transient receptor potential vanilloid type 4 (TRPV4), and the Na+-K+-2Cl- cotransporter (NKCC1) merit further investigation as potential targets in neurological diseases involving impaired brain fluid dynamics and elevated ICP.

Characterization of spinal cord diffusion tensor imaging metrics in clinically asymptomatic pediatric subjects with incidental congenital lesions

Study design

Retrospective study.

Objectives

To perform quantitative DTI measurements of the entire cervical and thoracic spinal cord (SC) in typically developing (TD) pediatric subjects with incidental findings of syringomyelia or hydromyelia on conventional MRI and in a TD population without any abnormalities.

Setting

USA.

Methods

26 TD recruited as part of large SC DTI study, four of these had incidental findings. Axial DTI images were acquired on 3T MR scanner to cover the cervical and thoracic SC. We performed group analysis of DTI values in the cord above and below the MR-defined lesion. For single-subject analysis, the cord above and below the lesion was compared to average values of TD population. A standard least squares regression model was used to compare DTI parameters fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) between TD population and subjects with hydromyelia and syringomyelia. A p value of 0.05 was used for statistical significance.

Results

In group analysis, MD and AD were significantly different in cord above the lesion in subjects with hydromyelia and syringomyelia (n = 4) compared to TD population (n = 22). For single-subject analysis, DTI parameters were significantly different in cord above the syringomyelia and below the syringomyelia; MD, AD, and RD were significantly different. A subject with hydromyelia showed significant difference in FA below the lesion.

Conclusions

This study demonstrates that DTI has the potential to be used as an imaging biomarker to evaluate SC above and below the congenital lesion in syringohydromyelia subjects.

Cell growth of immortalized arachnoid cells in the presence of fibroblasts and blood products

OBJECT

The pathophysiology of non-obstructive hydrocephalus involves alteration in cerebrospinal fluid (CSF) pathways. The exact mechanism is unknown, but as arachnoid CSF egress is a major route of CSF removal, damage or alteration to the growth of arachnoid cells may influence the rate of CSF absorption. We investigated the effect of soluble factors secreted by fibroblasts and the presence of blood products on arachnoid cell growth.

METHODS

An immortalized arachnoid cell line was developed and cells were grown on semipermeable membranes in a culture chamber. Arachnoid cells were plated in Transwells®, with fibroblasts separated from the arachnoid cells. Cell phenotype was analyzed and cell growth rates were determined by manual counts. Similar experiments were conducted with biliverdin, bilirubin, as well as fibroblast challenge. DNA content in the cell cultures was then determined as corroborative data. Cell counts for the additional arachnoid cell lines were calculated at each day and represented the controls.

RESULTS

Cell counts increased with each time point. Arachnoid cells in the three experimental conditions showed a statistically significant decrease in cell counts for each day when compared to the control group. Post hoc analysis showed differences between the control and experimental conditions but no significant difference between groups. The DNA content for each experimental condition was reduced at all time points when compared to the control arachnoid cells, but only became statistically significant at day 7.

CONCLUSION

Inflammation and hemorrhage are two common conditions associated with the development of hydrocephalus. The arachnoid membrane is exposed to fibroblasts and blood products (bilirubin, biliverdin) in these conditions, and their effect on arachnoid cell growth was studied. We have shown that arachnoid cell growth decreases in the presence of fibroblasts, bilirubin, and biliverdin. Given its intimate relationship with CSF, it is possible that the decreased growth of arachnoid cells may affect absorption and thus contribute to the development of hydrocephalus.

Evaluation of the flow of cerebrospinal fluid as well as gender and age characteristics in patients with communicating hydrocephalus, using phase-contrast magnetic resonance imaging

To determine the difference in the velocity parameters of cerebrospinal fluid flow in patients with varying severity of communicating hydrocephalus compared to a group of healthy volunteers without hydrodynamic disorders. The study involved 35 subjects with communicating hydrocephalus (25 subjects with Evans index of 0.31; 10 subject with Evans index of 0.46) and 62 healthy volunteers. The mean, volume, and peak flow velocities were determined at the different intracranial levels. Also were made an assessment of gender and age differences. Analysis of the differences between the mean values showed the progressive inhibition of cerebrospinal fluid outflow from the cranial cavity [in moderate communicating hydrocephalus-at 1.5 times (p < 0.05), in severe communicating hydrocephalus at 2-2.5 times (p < 0.01)], depending on the severity of enlargement of the ventricular system and, most likely, related to inhibition of its reabsorption. These changes may explain the clinical symptoms of subjects and serve as diagnostic criteria. Also it was revealed a significant influence of the factor of age on speed characteristics of the cerebrospinal fluid flow (F = 5.3303, p = 0.0003, for mean velocity).

Research into the Physiology of Cerebrospinal Fluid Reaches a New Horizon: Intimate Exchange between Cerebrospinal Fluid and Interstitial Fluid May Contribute to Maintenance of Homeostasis in the Central Nervous System

Cerebrospinal fluid (CSF) plays an essential role in maintaining the homeostasis of the central nervous system. The functions of CSF include: (1) buoyancy of the brain, spinal cord, and nerves; (2) volume adjustment in the cranial cavity; (3) nutrient transport; (4) protein or peptide transport; (5) brain volume regulation through osmoregulation; (6) buffering effect against external forces; (7) signal transduction; (8) drug transport; (9) immune system control; (10) elimination of metabolites and unnecessary substances; and finally (11) cooling of heat generated by neural activity. For CSF to fully mediate these functions, fluid-like movement in the ventricles and subarachnoid space is necessary. Furthermore, the relationship between the behaviors of CSF and interstitial fluid in the brain and spinal cord is important. In this review, we will present classical studies on CSF circulation from its discovery over 2,000 years ago, and will subsequently introduce functions that were recently discovered such as CSF production and absorption, water molecule movement in the interstitial space, exchange between interstitial fluid and CSF, and drainage of CSF and interstitial fluid into both the venous and the lymphatic systems. Finally, we will summarize future challenges in research. This review includes articles published up to February 2016.

The truth and coherence behind the concept of overdrainage of cerebrospinal fluid in hydrocephalic patients

INTRODUCTION

Overdrainage, siphoning, and slit-ventricle syndrome are well-documented complications of shunting in hydrocephalic patients. Despite the prevalence of these conditions, their mechanisms are still not fully understood. In this paper, the authors trace the concept of overdrainage and the related phenomena of siphoning and slit-ventricle syndrome.

PURPOSE

To provide a historical overview of overdrainage and to reignite discussion of a topic that has been settled.

METHODS AND RESULTS

A medical literature search and review were performed via Google Scholar. Of 565 publications, 3 primary papers were identified and a timeline was developed demonstrating the convergence of the aforementioned concepts. From the primary papers, 25 relevant publications were selected and further analyzed searching for hypothesis, evidence, and conclusions.

CONCLUSION

Overdrainage, siphoning, and slit-ventricle syndrome are associated concepts that have converged into a pathophysiological theory where siphoning of CSF leads to overdrainage, which is then hypothesized to cause slit-ventricle syndrome in a small subset of patients. Our data suggests that while there have been numerous reports regarding overdrainage and its consequences, the evidence is not as robust as currently presumed and this subject requires prospective exploration.

Increased CSF osmolarity reversibly induces hydrocephalus in the normal rat brain

BACKGROUND

Hydrocephalus is a central nervous system (CNS) disorder characterized by the abnormal accumulation of cerebrospinal fluid (CSF) in cerebral ventricles, resulting in their dilatation and associated brain tissue injury. The pathogenesis of hydrocephalus remains unclear; however, recent reports suggest the possible involvement of abnormal osmotic gradients. Here we explore the kinetics associated with manipulating CSF osmolarity on ventricle volume (VV) in the normal rat brain.

METHODS

CSF was made hyper-osmotic by introducing 10KD dextran into the lateral ventricle, either by acute injection at different concentrations or by chronic infusion at a single concentration. The induction and withdrawal kinetics of dextran infusion on VV were explored in both contexts.

RESULTS

Acute intraventricular injection of dextran caused a rapid increase in VV which completely reversed within 24 hours. These kinetics are seemingly independent of CSF osmolarity across a range spanning an order of magnitude; however, the magnitude of the transient increase in VV was proportional to CSF osmolarity. By contrast, continuous intraventricular infusion of dextran at a relatively low concentration caused a more gradual increase in VV which was very slow to reverse when infusion was suspended after five days.

CONCLUSION

We conclude that hyperosmolar CSF is sufficient to produce a proportional degree of hydrocephalus in the normal rat brain, and that this phenomenon exhibits hysteresis if CSF hyperosmolarity is persistent. Thus pathologically-induced increases in CSF osmolarity may be similarly associated with certain forms of clinical hydrocephalus. An improved understanding of this phenomenon and its kinetics may facilitate the development of novel therapies for the treatment of clinical hydrocephalus.

Hydrocephalus and arachnoid cysts

AIM

The management of arachnoid cysts (AC) remains controversial. An additional problem derives from the management of hydrocephalus associated with an AC. In this work, we discuss existing procedures proposed in the current literature for their treatment.

METHODS

We reviewed selected reports on intracranial ACs placing special interest in those about the association of hydrocephalus and ACs. We also briefly surveyed data of our patients with this association.

RESULTS AND DISCUSSION

Hydrocephalus is often found in midline and posterior fossa ACs. Interhemispheric lesions may also evolve with ventriculomegaly, while middle fossa lesions rarely produce hydrocephalus. Patients' age, cyst location and size, and macrocephaly have all been related to the development of hydrocephalus. Some authors remark on the role played by hydrocephalus and hypothesize that some ACs would result from disturbed cerebrospinal fluid (CSF) dynamics. They also propose that ACs might represent a localized form of hydrocephalus. We also comment on hydrocephalus in relation to the diverse locations of ACs. Neuroendoscopic techniques have transformed previous ways of management as cystoperitoneal shunting and open fenestration.

CONCLUSIONS

ACs may be pathogenetically related with hydrocephalus, and conversely, ACs may cause hydrocephalus. In some patients, aberrant CSF dynamics seems to play a major role in the development of both cyst and hydrocephalus. Hydrocephalus and ACs may be treated exclusively with neuroendoscopic procedures, although some patients will still require CSF shunting. The ideal option seems to consist of choosing the method that offers the highest success with a single procedure for treating the hydrocephalus and the AC simultaneously.

Risk factors associated with subdural hygroma after decompressive craniectomy in patients with traumatic brain injury : a comparative study

OBJECTIVE

Subdural hygroma (SDG) is a complication occurring after head trauma that may occur secondary to decompressive craniectomy (DC). However, the mechanism underlying SDG formation is not fully understood. Also, the relationship between the operative technique of DC or the decompressive effect and the occurrence and pathophysiology of SDG has not been clarified. Purpose of this study was to investigate the risk factors of SDG after DC in our series.

METHODS

From January 2004 to December 2008, DC was performed in 85 patients who suffered from traumatic brain injury. We retrospectively reviewed the clinical and radiological features. For comparative analysis, we divided the patients into 2 groups : one group with SDG after craniectomy (19 patients; 28.4% of the total sample), the other group without SDG (48 patients; 71.6%). The risk factors for developing SDG were then analyzed.

RESULTS

The mean Glasgow Outcome Scale (GOS) scores at discharge of the groups with and without SDG were 2.8 and 3.1, respectively (p<0.0001). Analysis of radiological factors showed that a midline shift in excess of 5 mm on CT scans was present in 19 patients (100%) in the group with SDG and in 32 patients (66.7%) in the group without SDG (p<0.05). An accompanying subarachnoid hemorrhage (SAH) was seen in 17 patients (89.5%) in the group with SDG and in 29 patients (60.4%) in the group without SDG (p<0.05). Delayed hydrocephalus accompanied these findings in 10 patients (52.6%) in the group with SDG, versus 5 patients (10.4%) in the group without SDG (p<0.05). On CT, compression of basal cisterns was observed in 14 members (73.7%) in the group with SDG and in 18 members of the group without SDG (37.5%) (p<0.007). Furthermore, tearing of the arachnoid membrane, as observed on CT, was more common in all patients in the group with SDG (100%) than in the group without SDG (31 patients; 64.6%) (p<0.05).

CONCLUSION

GOS showed statistically significant difference in the clinical risk factors for SDG between the group with SDG and the group without SDG. Analysis of radiological factors indicated that a midline shifting exceeding 5 mm, SAH, delayed hydrocephalus, compression of basal cisterns, and tearing of the arachnoid membrane were significantly more common in patients with SDG.

Symptomatic increased intracranial pressure due to arachnoid cysts

Intracranial arachnoid cysts are typically benign lesions, but rarely, they may cause signs and symptoms relating to increased intracranial pressure. We report 4 pediatric patients with arachnoid cysts who received successful surgical treatment after failing to respond to conservative medical therapies. After undergoing a shunting procedure, each patient experienced improvement in symptoms, resolution of optic disc swelling, and reduction or elimination of medications necessary to manage the condition. These cases illustrate the potential for arachnoid cysts to outstrip compensatory mechanisms and cause signs and symptoms requiring definitive surgical intervention.

Quantitative proteomics and metabolomics analysis of normal human cerebrospinal fluid samples

The analysis of cerebrospinal fluid (CSF) is used in biomarker discovery studies for various neurodegenerative central nervous system (CNS) disorders. However, little is known about variation of CSF proteins and metabolites between patients without neurological disorders. A baseline for a large number of CSF compounds appears to be lacking. To analyze the variation in CSF protein and metabolite abundances in a number of well-defined individual samples of patients undergoing routine, non-neurological surgical procedures, we determined the variation of various proteins and metabolites by multiple analytical platforms. A total of 126 common proteins were assessed for biological variations between individuals by ESI-Orbitrap. A large spread in inter-individual variation was observed (relative standard deviations [RSDs] ranged from 18 to 148%) for proteins with both high abundance and low abundance. Technical variation was between 15 and 30% for all 126 proteins. Metabolomics analysis was performed by means of GC-MS and nuclear magnetic resonance (NMR) imaging and amino acids were specifically analyzed by LC-MS/MS, resulting in the detection of more than 100 metabolites. The variation in the metabolome appears to be much more limited compared with the proteome: the observed RSDs ranged from 12 to 70%. Technical variation was less than 20% for almost all metabolites. Consequently, an understanding of the biological variation of proteins and metabolites in CSF of neurologically normal individuals appears to be essential for reliable interpretation of biomarker discovery studies for CNS disorders because such results may be influenced by natural inter-individual variations. Therefore, proteins and metabolites with high variation between individuals ought to be assessed with caution as candidate biomarkers because at least part of the difference observed between the diseased individuals and the controls will not be caused by the disease, but rather by the natural biological variation between individuals.

Quantitative proteomics and metabolomics analysis of normal human cerebrospinal fluid samples

The analysis of cerebrospinal fluid (CSF) is used in biomarker discovery studies for various neurodegenerative central nervous system (CNS) disorders. However, little is known about variation of CSF proteins and metabolites between patients without neurological disorders. A baseline for a large number of CSF compounds appears to be lacking. To analyze the variation in CSF protein and metabolite abundances in a number of well-defined individual samples of patients undergoing routine, non-neurological surgical procedures, we determined the variation of various proteins and metabolites by multiple analytical platforms. A total of 126 common proteins were assessed for biological variations between individuals by ESI-Orbitrap. A large spread in inter-individual variation was observed (relative standard deviations [RSDs] ranged from 18 to 148%) for proteins with both high abundance and low abundance. Technical variation was between 15 and 30% for all 126 proteins. Metabolomics analysis was performed by means of GC-MS and nuclear magnetic resonance (NMR) imaging and amino acids were specifically analyzed by LC-MS/MS, resulting in the detection of more than 100 metabolites. The variation in the metabolome appears to be much more limited compared with the proteome: the observed RSDs ranged from 12 to 70%. Technical variation was less than 20% for almost all metabolites. Consequently, an understanding of the biological variation of proteins and metabolites in CSF of neurologically normal individuals appears to be essential for reliable interpretation of biomarker discovery studies for CNS disorders because such results may be influenced by natural inter-individual variations. Therefore, proteins and metabolites with high variation between individuals ought to be assessed with caution as candidate biomarkers because at least part of the difference observed between the diseased individuals and the controls will not be caused by the disease, but rather by the natural biological variation between individuals.

Minimally invasive neurosurgery for cerebrospinal fluid disorders

This article focuses on minimally invasive approaches used to address disorders of cerebrospinal fluid (CSF) circulation. The author covers the primary CSF disorders that are amenable to minimally invasive treatment, including aqueductal stenosis, fourth ventricular outlet obstruction (including Chiari malformation), isolated lateral ventricle, isolated fourth ventricle, multiloculated hydrocephalus, arachnoid cysts, and tumors that block CSF flow. General approaches to evaluating disorders of CSF circulation, including detailed imaging studies, are discussed. Approaches to minimally invasive management of such disorders are described in general, and for each specific entity. For each procedure, indications, surgical technique, and known outcomes are detailed. Specific complications as well as strategies for their avoidance and management are addressed. Lastly, future directions and the need for structured outcome studies are discussed.

[Dynamic magnetic resonance imaging of the cerebrospinal fluid flow within the cerebral aqueduct by different FISP 2D sequences]

BACKGROUND/AIM

A vast majority of current radiogical techniques, such as computerized tomography (CT) and magnetic resonance imaging (MRI) have great potencial of vizualization and delineation of cerebrospinal fuid spaces morphology within cerebral aqueduct. The aim of this study was to determine the possibilities of two differently acquired FISP (Fast Imaging with Steady State Precession) 2D MR sequences in the estimation of the pulsatile cerebrospinal fluid (CSF) flow intensity through the normal cerebral aqueduct.

METHODS

Sixty eight volunteers underwent brain MRI on 1.5T MR imager with additionally performed ECG retrospectively gated FISP 2D sequences (first one, as the part of the standard software package, with following technical parameters: TR 40, TE 12, FA 17, Matrix: 192 x 256, Acq 1, and the second one, experimentally developed by our investigation team: TR 30, TE 12, FA 70, Matrix: 192 x 256, Acq 1) respectively at two fixed slice positions--midsagittal and perpendicular to cerebral aqueduct, displayed and evaluated by multiplegated images in a closed-loop cinematographic (CINE) format.

RESULTS

Normal brain morphology with preserved patency of the cerebral aqueduct in all of 68 healthy volunteers was demonstrated on MRI examination. Cerebrospinal fluid flow within the cerebral aqueduct was distinguishable on both CINE MRI studies in midsagittal plane, but the estimation of intraaqueductal CSF flow in perpendicular plane was possible on CINE MRI studies acquired with experimentally improved FISP 2D (TR 30, FA 70) sequence only.

CONCLUSION

Due to the changes of technical parameters CINE MRI study acquired with FISP 2D (TR 30, FA 70) in perpendicular plane demonstrated significantly higher capability in the estimation of the CSF pulsation intensity within the cerebral aqueduct.

Cerebrospinal fluid dynamics in the human cranial subarachnoid space: an overlooked mediator of cerebral disease. II. In vitro arachnoid outflow model

The arachnoid membrane (AM) and granulations (AGs) are important in cerebrospinal fluid (CSF) homeostasis, regulating intracranial pressure in health and disease. We offer a functional perspective of the human AM's transport mechanism to clarify the role of AM in the movement of CSF and metabolites. Using cultures of human AG cells and a specialized perfusion system, we have shown that this in vitro model mimics the in vivo characteristics of unidirectional fluid transport and we present the first report of serum-free permeability values (92.5 microl min(-1) mm Hg(-1) cm(-2)), which in turn are in agreement with the CSF outflow rates derived from a dynamic, in vivo magnetic resonance imaging-based computational model of the subarachnoid cranial space (130.9 microl min(-1) mm Hg(-1) cm(-2)). Lucifer yellow permeability experiments have verified the maintenance of tight junctions by the arachnoidal cells with a peak occurring around 21 days post-seeding, which is when all perfusion experiments were conducted. Addition of ruthenium red to the perfusate, and subsequent analysis of its distribution post-perfusion, has verified the passage of perfusate via both paracellular and transcellular mechanisms with intracellular vacuoles of approximately 1 microm in diameter being the predominant transport mechanism. The comparison of the computational and in vitro models is the first report to measure human CSF dynamics functionally and structurally, enabling the development of innovative approaches to modify CSF outflow and will change concepts and management of neurodegenerative diseases resulting from CSF stagnation.

Differential diagnosis of T2 hyperintense spinal cord lesions: part B

Hyperintense spinal cord signal on T2-weighted images is seen in a wide-ranging variety of spinal cord processes. Causes including simple MR artefacts, trauma, primary and secondary tumours, radiation myelitis and diastematomyelia were discussed in Part A. The topics discussed in Part B of this two part series include multiple sclerosis, subacute combined degeneration of the spinal cord, cord infarction, arteriovenous shunts, transverse myelitis, neurosarcoidosis, AIDS-associated vacuolar myelopathy, and syringohydromyelia. Characterization of the abnormal areas of T2 signal as well as their appearance on other MR imaging sequences, when combined with clinical context and laboratory investigations, will often allow a unique diagnosis, or at least aid in narrowing the differential diagnosis. A wide range of instructive cases is discussed here, with review of the published reports focusing on pertinent MR features to aid in diagnosis.

Dynamics of subdural hygroma following decompressive craniectomy: a comparative study

Object

This retrospective comparative cohort study was aimed at discovering the risk factors associated with subdural hygroma (SDG) following decompressive craniectomy (DC) to relieve intracranial hypertension in severe head injury.

Methods

Sixty-eight of 104 patients who had undergone DC during a 48-month period and survived > 30 days were eligible for this study. To assess the dynamics of subdural fluid collections, the authors compared CT scanning data from and the characteristics of 39 patients who had SDGs with the data in 29 patients who did not have hygromas. Variables significant in the appearance, evolution, and resolution of this complication were analyzed in a 36-week longitudinal study.

Results

The earliest imaging evidence of SDG was seen during the 1st week after DC. The SDG volume peaked between Weeks 3 and 4 post-DC and was gradually resolved by the 17th week. Among the mechanisms of injury, motor vehicle accidents were most often linked to the development of an SDG after DC (p < 0.0007), and falls were least often associated (p < 0.005). Moreover, patients with diffuse brain injury were more prone to this complication (p < 0.0299) than those with an evacuated mass (p < 0.0001). There were no statistically significant differences between patients with and without hygromas in terms of age, sex, Glasgow Coma Scale score, intraventricular and subarachnoid hemorrhage, levels of intracranial pressure and cerebral perfusion pressure, timing of decompression, and the need for CSF diversion. More than 90% of the SDGs were ipsilateral to the side of the craniectomy, and 3 (8%) of 39 SDGs showed evidence of internal bleeding at ~ 8 weeks postinjury. Surgical evacuation was needed in 4 patients with SDGs.

Conclusions

High dynamic accidents and patients with diffuse injury were more prone to SDGs. Close to 8% of SDGs converted themselves into subdural hematomas at ~ 2 months postinjury. Although SDGs developed in 39 (~ 60%) of 68 post-DC patients, surgical evacuation was needed in only 4.

A contemporary definition and classification of hydrocephalus

This review focuses on the problems related to defining hydrocephalus and on the development of a consensus on the classification of this common problem. Such a consensus is needed so that diverse research efforts and plans of treatment can be understood in the same context. The literature was searched to determine the definition of hydrocephalus and to identify previously proposed classification schemes. The historic perspective, purpose, and result of these classifications are reviewed and analyzed. The concept of the hydrodynamics of cerebrospinal fluid (CSF) as a hydraulic circuit is presented to serve as a template for a contemporary classification scheme. Finally, a definition and classification that include all clinical causes and forms of hydrocephalus are suggested. The currently accepted classification of hydrocephalus into "communicating" and "noncommunicating" varieties is almost 90 years old and has not been modified despite major advances in neuroimaging, neurosciences, and treatment outcomes. Despite a thorough search of the literature using computerized search engines and bibliographies from review articles and book chapters, I identified only 6 previous attempts to define and classify different forms of hydrocephalus. This review proposes the following definition for hydrocephalus: hydrocephalus is an active distension of the ventricular system of the brain related to inadequate passage of CSF from its point of production within the ventricular system to its point of absorption into the systemic circulation. Based on this definition (potential points of flow restriction) and on the view of the CSF system as a hydraulic circuit, a classification system is proposed. The acceptance of this proposed definition and classification schema would allow clinicians and basic scientists to communicate effectively, to share information and results, and to develop testable hypotheses.

Mounting device for external cerebrospinal fluid drainage: the Freiburg Stativ

BACKGROUND

External drainage of cerebrospinal fluid (CSF) is one of the most common neurosurgical procedures. It is important to maintain a stable drainage rate, but with the commonly available mountings for CSF drainage this can be difficult to achieve. The drainage rate is dependent on the height-difference between the CSF space and the drip chamber of the device. Most mountings for open CSF drainage cannot be satisfactorily fixed at the bed of the patient; especially if the head of the bed is moved, there is a risk of over- or underdrainage.

MATERIALS AND METHODS

We have therefore constructed a mounting for open CSF drainage which allows appropriate adjustment of the rate of CSF outflow, even if the patient's head part of the bed is moved.

FINDINGS

The device was easily mountable or exchangeable at any hospital bed and served equally well for ventricular or for lumbar drainage.

CONCLUSION

We think that this device can help to reduce serious complication of over- or underdrainage in external CSF drainage.

The definition and classification of hydrocephalus: a personal recommendation to stimulate debate

The aim of this review is to refine the definition and classification of hydrocephalus as a preview to developing an international consensus on the nomenclature of this complex condition. This proposed definition and classification is based on my own work in this area and is intended to promote a debate on the concepts presented.

A literature review of contemporary definitions and classifications of hydrocephalus, and of the historic context in which these concepts developed, is presented. Based on new technology and understanding of hydrocephalus, the rationale for nomenclature is also discussed.

Currently, there is no recognized definition of hydrocephalus. The failure to agree on a working definition impedes progress in understanding the pathophysiology and treatment of hydrocephalus. There are many proposed classifications, each with its own starting point in terms of the definition of the condition. This author recommends that the following definition be used as a starting point to develop a consensus statement defining hydrocephalus: "Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of cerebrospinal fluid from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation." Such a definition can be used to develop a rational classification consistent with observations from contemporary neuroimaging and can lead to testable hypotheses. It is concluded that hydrocephalus is a complicated neurologic disorder with many causes and methods of treatment. Clinicians and basic scientists must agree on a working definition of the condition to be able to interpret results from different investigators. Reaching a consensus on a working definition and functional classification should be a high priority for researchers in this field.

New concept of cerebrospinal fluid dynamics in cerebral venous sinus thrombosis

Cerebral venous sinus thrombosis develops as a consequence of sinus obstruction, leading to hindering of venous drainage, gradual edema and increased intracranial pressure (ICP). Intracerebral hemorrhage occurs, of which the symptoms may be alleviated by cerebrospinal fluid (CSF) drainage. Clinical brain function improvement may be directly attributed to the effect of the decreased ICP, or to the decreased pressure on the venous sinus which alleviates venous blood flow and sinus thrombosis. However, worsening, rather than improvement of symptoms are occasionally observed in patients after CSF drainage, and therefore it is as yet difficult to determine the precise indications for CSF drainage. The authors of this study suggest that external CSF drainage of sagittal sinus thrombosis may accelerate the sinus thrombosis and aggravate symptoms in such a patient. In other words, the sagittal sinus differs from other sinuses in that when sinus thrombosis develops, CSF absorption is impeded from the early stages, leading to a higher likelihood of ventricular dilatation, because most of the CSF are normally absorbed through the arachnoid villi and drain into the sagittal sinus. External CSF drainage and subsequently decreased ICP will improve sinus thrombosis after implementation of CSF drainage of the sagittal sinus thrombosis, but on the other hand, this decreased CSF drainage leads to decreased venous sinus blood flow, both of which may result in aggravation of the sinus thrombosis. However, it is also suggested that CSF drainage may be accomplished safely on the unilateral lateral sinus thrombosis because CSF drainage may alleviate venous sinus obstruction, and does not influence the sinus blood flow. We, authors of this study suggest that caution should be taken when external CSF drainage of the sagittal sinus thrombosis is performed to prevent further aggravation of intracranial pressure elevation.

Normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is a reversible disorder characterized by gait impairment, subcortical dementia, and urinary urgency and incontinence associated with impaired cerebrospinal fluid circulation and ventriculomegaly. Treatment with shunt surgery is most likely to increase mobility, and may also improve dementia and urinary symptoms. An international, independent study group recently published guidelines for the diagnosis and management of idiopathic NPH. This article helps geriatricians identify patients who might have NPH, and care for these patients after shunt placement.

Accelerated progression of kaolin-induced hydrocephalus in aquaporin-4-deficient mice

Hydrocephalus is caused by an imbalance in cerebrospinal fluid (CSF) production and absorption, resulting in excess ventricular fluid accumulation and neurologic impairment. Current therapy for hydrocephalus involves surgical diversion of excess ventricular fluid. The water-transporting protein aquaporin-4 (AQP4) is expressed at the brain-CSF and blood-brain barriers. Here, we provide evidence for AQP4-facilitated CSF absorption in hydrocephalus by a transparenchymal pathway into the cerebral vasculature. A mouse model of obstructive hydrocephalus was created by injecting kaolin (2.5 mg/mouse) into the cisterna magna. Intracranial pressure (ICP) was approximately 5 mm Hg and ventricular size <0.3 mm(3) in control mice. Lateral ventricle volume increased to 3.7+/-0.5 and 5.1+/-0.5 mm(3) in AQP4 null mice at 3 and 5 days after injection, respectively, significantly greater than 2.6+/-0.3 and 3.5+/-0.5 mm(3) in wildtype mice (P<0.005). The corresponding ICP was 22+/-2 mm Hg at 3 days in AQP4 null mice, significantly greater than 14+/-1 mm Hg in wildtype mice (P<0.005). Brain parenchymal water content increased by 2% to 3% by 3 days, corresponding to approximately 50 muL of fluid, indicating backflow of CSF from the ventricle into the parenchymal extracellular space. A multi-compartment model of hydrocephalus based on experimental data from wildtype mice accurately reproduced the greater severity of hydrocephalus in AQP4 null mice, and predicted a much reduced severity if AQP4 expression/function were increased. Our results indicate a significant role for AQP4-mediated transparenchymal CSF absorption in hydrocephalus and provide a rational basis for evaluation of AQP4 induction as a nonsurgical therapy for hydrocephalus.

Extensive hydromyelia

Hydromyelia is frequently associated with dissociated sensory loss, scoliosis, and upper limb weakness. This report describes the case of a 9-year old male with an extensive hydromyelia associated with a spinal cord tumor and an oligosymptomatic clinical presentation.

Pseudotumor cerebri: disordered cerebrospinal fluid hydrodynamics with extra-axial CSF collections

Pseudotumor cerebri is uncommon in the pediatric age group and presents with clinical characteristics different from the adult form. We report a 5-year-old boy who presented with--seemingly spontaneous--alternating subdural CSF collections before progressing to develop pseudotumor cerebri. To our knowledge, this is the first report of such a presentation. In the prepubertal pediatric age group, pseudotumor cerebri may be associated with multiple etiologic factors (more than in the adult population). The exact common mechanism behind such a disorder is not known. Pseudotumor cerebri may be a disorder of CSF hydrodynamics. It may also be linked to other disorders of CSF hydrodynamics, as in our case. The exact link and mechanistic differences between these apparently related disorders deserve further analysis and investigation, possibly through dynamic MRI techniques.

Influence of neuroendoscopic third ventriculostomy on the size of ventricles in chronic hydrocephalus

Our intention was to compare the clinical outcome after surgical treatment of chronic hydrocephalus between patients who were subjected to neuroendoscopic third ventriculostomy and patients who underwent shunt implantation. At the Department of Neurosurgery of the Research Institute of Polish Mothers' Memorial Hospital from 1999 to 2001, 29 children, of an average age of 7 years (+/-7.1 years SD), underwent successful neuroendoscopic procedures, and from 1992 to 1994, 59 children, of an average age of 2 months (+/-1.9 months SD), underwent shunt implantation. The size of the ventricular system was described by the Frontal Horn Index and its change after operative procedures by the ratio of the final to the primary Frontal Horn Index. Head circumference was measured in percentiles according to the Kurniewicz-Witczakowa chart for Polish children. The reduction in head circumference after a neuroendoscopic procedure was, on average, significantly less than after a shunt implantation (0.39 percentiles +/-29.6 SD vs 17.93 percentiles +/-19.93 SD). Concerning the change in ventricular size after a neuroendoscopic procedure, it was noticed that the average ratio of the final to the primary Frontal Horn Index was 0.9. Meanwhile, the same parameter after a shunt implantation was 0.55. Based on the values of the Frontal Horn Indexes, it was observed that the ventricular system in infants after neuroendoscopic procedures was significantly larger than in other age groups (0.7 vs 0.5). After successful neuroendoscopic operations in a group of children suffering from Chiari II malformation, ventricular systems were slightly enlarged. The ratio of the final Frontal Index to the primary Frontal Horn Index was 1.31. In children suffering from chronic hydrocephalus, the average reduction in the size of the ventricular system and the rate of head circumference growth are lower after neuroendoscopic operations than after shunt implantations. Successful neuroendoscopic procedures are characterized by, on average, a higher rate of head circumference growth in infants than in neonates. In addition, the rate of head circumference growth after successful neuroendoscopic procedures could be higher than before the operation, which is clearly visible in children suffering from Chiari II malformation, but it does not mean a constant increase of that parameter during the postoperative period.

Effectiveness of neuroendoscopic procedures in the treatment of complex compartmentalized hydrocephalus in children

OBJECTIVE

The main object of the work is to assess the suitability of neuroendoscopic techniques for the treatment of complex compartmentalized hydrocephalus.

METHODS

For this purpose the authors compared two groups of children treated in the Research Institute of the Polish Mother's Memorial Hospital from March 1997 to January 2002. The first group of 47 children, treated using neuroendoscopic procedures, was compared with the second, which comprised 80 children treated conventionally by complicated shunt implantations.

RESULTS

The children treated neuroendoscopically needed on average 1.7660 procedures during the entire therapy, and 1.0232 operations a year. The same parameters in the conventionally-treated group were as follows: the total number of procedures was 7.050, and the rate of reoperation was 3.949 procedures a year. The proportion of patients who suffered from complications connected with operative treatment and who had a bad outcome was higher in the conventionally-treated group than in the neuroendoscopic one.